1. Field of the Invention
The present invention relates to a system and method to exchange information relating to mobility management during an inter-access handover, more particularly, a system and method to exchange information when an inter-access handover occurs during an ongoing policy and/or charging controlled session.
2. Description of the Related Art
A Next Generation Network (NGN) IP Multimedia Subsystem (IMS) supports provision of Sessions Initiation Protocol (SIP)-based multimedia services to NGN terminals. IMS also supports the provision of Public Switched Telephony Network (PSTN)/Integrated Services Digital Network (ISDN) simulation services. Various access technologies may be used to access IMS, for example, General Packet Radio Service (GPRS), Digital Subscriber Line (xDSL), and Wireless Local Area Network (WLAN). Policy control functions have been standardized for the GPRS access (in 3rd Generation Partnership Project (3GPP) known as Policy Decision Function (PDF) or as Policy and Charging Rules Function (PCRF), when charging control is included), are being standardized for, at least, the WLAN access.
In general, a system structure of a communication network is such that a subscriber's user equipment, such as a mobile station, a mobile phone, a fixed phone, a personal computer (PC), a laptop, a personal digital assistant (PDA) or the like, is connected via transceivers and interfaces, such as an air interface, a wired interface or the like, to an access network. subsystem. The access network subsystem controls the communication connection to and from the user equipment and is connected via an interface to a corresponding core or backbone network subsystem. The core (or backbone) network subsystem switches data transmitted via the communication connection to a destination, such as another user equipment, a service provider (server/proxy), or another communication network. It is to be noted that the core network subsystem may be connected to a plurality of access network subsystems. Depending on the used communication network, the actual network structure may vary, as known for those skilled in the art and defined in respective specifications, for example, for Universal Mobile Telecommunications System (UMTS), Global System for Mobile Communication (GSM) and the like.
Generally, for properly establishing and handling a communication connection between network elements such as the user equipment and another user equipment, a database, a server, etc., one or more intermediate network elements such as support nodes or service nodes are involved. One or more connection parameters are used for defining connection characteristics. This includes, for example, a packet based data transmission protocol information, such as a PDP (Packet Data Protocol) context information, for example, information about quality of service (QoS) requested or provided, charging-related information, such as a charging class, etc. IMS specific information, Authorization Token or UE IP address or user/UE identity and Flow ID(s) are used as binding information when requesting QoS authorization for a PDP context.
When the communication connection is initialized, an authorization for the connection parameters of services is requested from a policy control entity which decides on connection parameters to be authorized for the communication connection and on service types which can be provided for the communication connection.
Both, push and pull modes may be used for obtaining an authorization decision from a policy decision function (PDF/Service Policy Decision Function (SPDF)/PCRF) to a gateway. In a push operation, the PDF sends the information without being requested by the gateway. In a pull operation, the gateway requests the PDF to send the information to the gateway.
When a typical inter-access handover, that is, a handover from a Digital Subscriber Line (xDSL) access to General Packet Radio Service (GPRS) access or vice versa, occurs during an ongoing policy and/or charging controlled session, the policy control entity changes. Accordingly, problems occur in which a session control element, such as a Proxy Call Session Control Function (P-CSCF) in IMS or an Application Function (AF), needs to determine or identify a new policy control entity. A system and method are needed that would allow the AF/P-CSCF to obtain an IP address of the new PCRF. The system and method would allow the new policy control entity to obtain session related parameters for making an authorization decision for a new session, to obtain subscriber or service specific parameters, and/or to find the new gateway. The new gateway would need to be provided the ability to find the application function used by the session. Also, for an existing session being transferred, the system and method would need to provide the policy control entity the ability to obtain an already made authorization decision.